Which of the following statements is incorrect about later Vedic and post-Vedic periods?
a) The evidence of asramas or stages of life comes from later Vedic texts.
b) The concept of the asramas was firmly established during the age of the Dharmasutras.
c) The concept of four stages of life is applicable to all the four varnas.
d) The whole life of an individual was divided into a series of samskaras or sacraments.